Conventional microwave amplifiers use an FET with a common source. The input signal is applied to the gate and the amplified signal is output on the drain. Since feedback is from the output of the common source stage, a low impedance point, a low feedback resistance value must be used. The feedback resistor is usually about 150.OMEGA. to 200.OMEGA.. This results in increased feedback, and therefore reduced gain and output power. Additionally, the noise figure of the amplifier is higher than would exist if a higher feedback resistance value is used.
As is described in Vendelin et al., Microwave Circuit Design Using Linear and Nonlinear Techniques, John-Wiley & Sons, 1990, pp. 250, 252, cascade circuits using bipolar transistors and resistive feedback with an output transformer are known. Such circuit is operable only at comparatively low frequencies, is subject to the higher output impedance of the bipolar transistors, requiring large impedance transformation at the output, and will not have the desired operation with the feedback resistor connected to the collector of the common-base transistor.
There is therefore a need for a monolithic microwave integrated single-stage amplifier circuit having a low noise figure, improved gain and increased power output.